I am able to capture text from web pages just fine in Safari, either using the keyboard shortcut or the Services menu. However, I can’t capture selected text as RTF from FF3 - the key strokes don’t work, and the EagleFiler option is grayed out in the Services menu.
“Capture” is a specific term that means importing using EagleFiler’s capture key. In a Web browser, this will import the whole page.
What you are referring to is called the “EagleFiler: Import” service. None of your other services are enabled, either. This is because Firefox does not support Mac OS X’s services feature. You can import selected text from Firefox via drag and drop. To use a keystroke, you would need to use a browser that supports services.